Maharaja Manindra Chandra College

Kolkata, India

Maharaja Manindra Chandra College

Kolkata, India

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Guha A.,University of Calcutta | Banu K.S.,University of Calcutta | Banerjee A.,University of Calcutta | Ghosh T.,University of Calcutta | And 3 more authors.
Journal of Molecular Catalysis A: Chemical | Year: 2011

Three new mono-manganese(II) complexes of a compartmental ligand, namely [Mn(HL)(H2O)3](NO3)2·H 2O (1), [Mn(HL)(SCN)2(H2O)]·H 2O (2), and [Mn(HL){N(CN)2}(H2O) 2](NO3)·H2O (3), where L = 2,6-bis{2-(N-ethyl)pyridineiminomethyl}-4-methylphenolato, have been synthesized and characterised by routine physicochemical techniques and complexes 1, 2 also by X-ray single crystal structure analysis. All the mono nuclear complexes contain MnII high spin species at octahedral core as evidenced by magnetic moment (measured at 300 K) and EPR study at 77 K. As revealed by crystal structure analyses, the protonation of one imine nitrogen atom of the potential dinucleating ligand L hampers to form the expected dinuclear Mn II complex. However, complexes 1-3 show excellent catecholase-like activity with both 3,5-di-tert-butylcatechol and tetrachlorocatechol as substrates. In addition complexes 1 and 2 also exhibit phosphatase activity, while 3 forms an adduct with p-nitrophenyl phosphate as substrate. To the best of our knowledge this is the first report of MnII complexes being able to catalyze the oxidation of TCC to TCQ. Catecholase and phosphatase activities have been monitored by UV-vis spectrophotometer and Michaelis-Menten equation has been applied to rationalize all the kinetic parameters where complex 1 shows maximum kcat value followed by 2 and 3 (where for phosphatase activity 3 only forms an adduct). © 2011 Elsevier B.V. All rights reserved.


Sasmal S.,University of Calcutta | Hazra S.,University of Calcutta | Kundu P.,Maharaja Manindra Chandra College | Majumder S.,University of Calcutta | And 3 more authors.
Inorganic Chemistry | Year: 2010

The work in this paper aims to portray a complete structural, magnetic, and theoretical description of two original endto-end (EE)μ1,3-azide- bridged, cyclic tetranuclear NiII clusters, [{NiII(L 1)(M1,3-N3)(H2O)}4] (1) and [{NiII(L2)(μ1,3-N3)(H 2O)}4] (2), where the ligands used to achieve these species, HL1 and HL2, are the tridentate Schiff base ligands obtained from [1 + 1] condensations of salicylaldehyde with 1-(2-aminoethyl)-piperidine and 4-(2-aminoethyl)-morpholine, respectively. The title compounds, 1 and 2, crystallize in a monoclinic P21 space group. Overall, both species can be described in a similar way; where all NiII centers within each molecule are hexacoordinated and bound to [L1]- or [L2]- through the phenoxo oxygen, imine nitrogen, and piperidine/morpholine nitrogen atoms of the corresponding ligand. The remaining coordination sites are satisfied by one molecule of H2O and two nitrogen atoms from N3 - anions. The latest act as bridges between NiII ions, and eventually, only four azido groups are linked to the same number of NiII centers resulting in the formation of cyclic NiII 4 systems. Interestingly, compounds 1 and 2 are the two sole examples of tetranuclear clusters generated exclusively by EE azide-bridging ligands to date. All the N(azide)-Ni-N(azide) moieties are almost linear in 1 and 2 indicating trans arrangement of the azido ligand. Variable-temperature (2-300 K) magnetic susceptibilities of 1 and 2 have been measured under magnetic fields of 0.04 T (from 2 to 30 K) and 0.7 T (from 30 to 300 K), and magneto-structural correlations have been performed. Despite the presence of both ferromagnetic and antiferromagnetic interactions in both compounds, significant differences have been observed in their magnetic behaviors directly related to the arrangement of the bridging azido ligands. Hence, compound 1 has an overall moderate antiferromagnetic behavior due to the presence of an exchange pathway with an unprecedented Ni-N · · · N-Ni torsion angle close to 0°, meanwhile complex 2 exhibits a predominant ferromagnetic behavior, with torsion angles between 50 and 90°. Density functional theory calculations have been performed to provide more insight into the magnetic nature of this new family of NiII-azido complexes and also to corroborate the fitting of the data. © 2010 American Chemical Society.


Sasmal S.,University of Calcutta | Hazra S.,University of Calcutta | Kundu P.,Maharaja Manindra Chandra College | Dutta S.,Indian Association for The Cultivation of Science | And 3 more authors.
Inorganic Chemistry | Year: 2011

This investigation presents the syntheses, crystal structures, magnetic properties, and density functional theoretical modeling of magnetic behavior of two heterobridged μ-phenoxo-μ 1,1-azido dinickel(II) compounds [Ni II 2(L 1) 2(μ 1,1- N 3)(N 3)(H 2O)]•CH 3CH 2OH (1) and [Ni II 2(L 2) 2(μ 1,1-N 3)(CH 3CN)(H 2O)](ClO 4)•H 2O•CH 3CN (2), where HL 1 and HL 2 are the [1 + 1] condensation products of 3-methoxysalicylaldehyde and 1-(2-aminoethyl)-piperidine (for HL 1)/4-(2-aminoethyl)-morpholine (for HL 2), along with density functional theoretical magneto-structural correlations of μ-phenoxo-μ 1,1-azido dinickel(II) systems. Compounds 1 and 2 crystallize in orthorhombic (space group Pbca) and monoclinic (space group P2 1/c) systems, respectively. The coordination environments of both metal centers are distorted octahedral. The variable-temperature (2-300 K) magnetic susceptibilities at 0.7 T of both compounds have been measured. The interaction between the metal centers is moderately ferromagnetic; J = 16.6 cm -1, g = 2.2, and D = -7.3 cm -1 for 1 and J = 16.92 cm -1, g = 2.2, and D(Ni1) = D(Ni2) = -6.41 cm -1 for 2. Broken symmetry density functional calculations of exchange interaction have been performed on complexes 1 and 2 and provide a good numerical estimate of J values (15.8 cm -1 for 1 and 15.35 cm -1 for 2) compared to experiments. The role of Ni-N bond length asymmetry on the magnetic coupling has been noted by comparing the structures and J values of complexes 1 and 2 together with previously published dimers 3 (Eur. J. Inorg. Chem. 2009, 4982), 4 (Inorg. Chem. 2004, 43, 2427), and 5 (Dalton Trans. 2008, 6539). Our extensive DFT calculations reveal an important clue to the mechanism of coupling where the orientation of the magnetic orbitals seems to differ with asymmetry in the Ni-N bond lengths. This difference in orientation leads to a large change in the overlap integral between the magnetic orbitals and thus the magnetic coupling. DFT calculations have also been extended to develop several magneto-structural correlations in this type of complexes and the correlation aim to focus on the asymmetry of the Ni-N bond lengths reveal that the asymmetry plays a proactive role in governing the magnitude of the coupling. From a completely symmetric Ni-N bond length, two behaviors have been noted: with a decrease in bond length there is an increase in the ferromagnetic coupling, while an increase in the bond lengths leads to a decrease in ferromagnetic interaction. The later correlation is supported by experiments. The magnetic properties of 1, 2, and three previously reported related compounds have been discussed in light of the structural parameters and also in light of the theoretical correlations determined here. © 2011 American Chemical Society.


Majumdar L.,Indian Center for Space Physics | Das A.,Indian Center for Space Physics | Chakrabarti S.K.,Indian Center for Space Physics | Chakrabarti S.K.,Sn Bose National Center For Basic Science | And 2 more authors.
New Astronomy | Year: 2013

We carry out a quantum chemical calculation to obtain the infrared and electronic absorption spectra of several complex molecules of the interstellar medium (ISM). These molecules are the precursors of adenine, glycine & alanine. They could be produced in the gas phase as well as in the ice phase. We carried out a hydro-chemical simulation to predict the abundances of these species in the gas as well as in the ice phase. Gas and grains are assumed to be interacting through the accretion of various species from the gas phase onto the grain surface and desorption (thermal evaporation and photo-evaporation) from the grain surface to the gas phase. Depending on the physical properties of the cloud, the calculated abundances varies. The influence of ice on vibrational frequencies of different pre-biotic molecules was obtained using Polarizable Continuum Model (PCM) model with the integral equation formalism variant (IEFPCM) as default SCRF method with a dielectric constant of 78.5. Time dependent density functional theory (TDDFT) is used to study the electronic absorption spectrum of complex molecules which are biologically important such as, formamide and precursors of adenine, alanine and glycine. We notice a significant difference between the spectra of the gas and ice phase (water ice). The ice could be mixed instead of simple water ice. We have varied the ice composition to find out the effects of solvent on the spectrum. We expect that our study could set the guidelines for observing the precursor of some bio-molecules in the interstellar space. © 2012 Elsevier B.V. All rights reserved.


Das A.,Indian Center for Space Physics | Majumdar L.,Indian Center for Space Physics | Chakrabarti S.K.,Indian Center for Space Physics | Chakrabarti S.K.,Sn Bose National Center For Basic Science | And 2 more authors.
New Astronomy | Year: 2013

Chemical composition of a molecular cloud is highly sensitive to the physical properties of the cloud. In order to obtain the chemical composition around a star forming region, we carry out a two dimensional hydrodynamical simulation of the collapsing phase of a proto-star. A total variation diminishing scheme (TVD) is used to solve the set of equations governing hydrodynamics. This hydrodynamic code is capable of mimicking evolution of the physical properties during the formation of a proto-star. We couple our reasonably large gas-grain chemical network to study the chemical evolution during the collapsing phase of a proto-star. To have a realistic estimate of the abundances of bio-molecules in the interstellar medium, we include the recently calculated rate coefficients for the formation of several interstellar bio-molecules into our gas phase network. Chemical evolution is studied in detail by keeping grain at the constant temperature throughout the simulation as well as by using the temperature variation obtained from the hydrodynamical model. By considering a large gas-grain network with the sophisticated hydrodynamic model more realistic abundances are predicted. We find that the chemical composition are highly sensitive to the dynamic behavior of the collapsing cloud, specifically on the density and temperature distribution. © 2013 Elsevier B.V. All rights reserved.


Ghosh A.,Presidency University of India | Chakrabarti S.,Presidency University of India | Biswas K.,Presidency University of India | Biswas K.,Maharaja Manindra Chandra College | Ghosh U.C.,Presidency University of India
Applied Surface Science | Year: 2014

Hydrous Ce(IV)-Zr(IV) oxide (Ce/Zr ∼ 1:1, mol/mol) (HCZMO) prepared by simple chemical precipitation was nanoparticles (60-70 nm) agglomerate with irregular surface morphology. The BET surface area, pore volume and pH zpc were estimated to be 185.04 m2 g-1, 0.1219 cm3 g-1 and 5.8 (±0.2), respectively. Investigation of fluoride adsorption over HCZMO from its aqueous phase at an optimized pH ∼ 6.0 showed that the adsorption kinetics and equilibrium data described, respectively, the pseudo-second order equation (R2 = 0.98-0.99) and the Langmuir isotherm (R2 > 0.99) very well. Values of the computed Arrhenius activation energy, Ea (1.16 kJ mol-1), Langmuir monolayer capacity, θ (19.5 mg g-1), D-R adsorption energy, ED-R (15.05 kJ mol-1) and isosteric heat of reaction, ΔHr (0.518 kJ mol-1) suggested that the fluoride has high affinity for homogeneous HCZMO surface for adsorption. Evidences appeared from the equal distribution co-efficient values and too well Langmuir isotherm fit. The fluoride adsorption reactions at 298-313 K with HCZMO were spontaneous (ΔG0 = negative) despite endothermic nature (ΔH0, kJ mol-1 = +3.53, +4.04), owing to the increase of entropy (ΔS0, J mol-1 K-1 = +12.4, 13.8). More than 95% fluoride was released from F-HCZMO (24.8 mg F- g-1) by 1.0 M NaOH, confirming the ion-exchange adsorption mechanism inclining to chemisorption. 1 g HCZMO per liter of a groundwater (F-: 4.40 mg L-1) can reduce fluoride level below 1.5 mg L-1 in batch treatment. © 2014 Elsevier B.V. All rights reserved.


Ghosh O.,Seth Anandram Jaipuria College | Ghosh T.,Maharaja Manindra Chandra College | Chatterjee T.N.,Dinabandhu Andrews College
Solar Physics | Year: 2014

We studied the predictability of the 10.7 cm solar radio flux by using stationary and non-stationary time-series analysis techniques of fractal theory to find the correlation exponent, the spectral exponent, the Hurst exponent, and the fluctuation exponent of the time series. The Hurst exponent was determined, from which the fractal dimension and consequently the predictability was evaluated. The results suggest that stationary methods of analysis yield inconsistent result, that is, amongst the four techniques used, the values of the exponents show great disparity. While two of the techniques, namely the auto-correlation function analysis and the spectral analysis, indicate long-term positive correlation, the other two methods, specifically the Hurst rescaled range-analysis and the fluctuation analysis, clearly exhibit the anti-correlated nature of the time series. The two non-stationary methods, that is, the discrete wavelet transform and the centered moving-average analysis, yielded values of the Hurst exponent that are indicative of positive correlation, of persistent behavior, and also showed that the time series is predictable to a certain extent. © 2013 Springer Science+Business Media Dordrecht.


Majumdar L.,Indian Center for Space Physics | Das A.,Indian Center for Space Physics | Chakrabarti S.K.,Indian Center for Space Physics | Chakrabarti S.K.,se National Center For Basic Science | And 2 more authors.
Research in Astronomy and Astrophysics | Year: 2012

One of the stumbling blocks for studying the evolution of interstellar molecules is the lack of adequate knowledge about the rate coefficients of various reactions which take place in the interstellar medium and molecular clouds. Some theoretical models of rate coefficients do exist in the literature for computing abundances of complex pre-biotic molecules. So far these have been used to study the abundances of these molecules in space. However, in order to obtain more accurate final compositions in these media, we have calculated the rate coefficients for the formation of some of the most important interstellar pre-biotic molecules by using quantum chemical theory. We use these rates inside our hydro-chemical model to examine the chemical evolution and final abundances of pre-biotic species during the collapsing phase of a proto-star. We find that a significant amount of various pre-biotic molecules could be produced during the collapse phase of a proto-star. We thoroughly study the formation of these molecules via successive neutral-neutral and radical-radical/radical-molecular reactions. We present the time evolution of the chemical species with an emphasis on how the production of these molecules varies with the depth of a cloud. We compare the formation of adenine in interstellar space using our rate-coefficients and using those obtained from existing theoretical models. Formation routes of the pre-biotic molecules are found to be highly dependent on the abundances of the reactive species and the rate coefficients involved in the reactions. The presence of grains strongly affects the abundances of the gas phase species. We also carry out a comparative study between different pathways available for the synthesis of adenine, alanine, glycine and other molecules considered in our network. Despite the huge abundances of the neutral reactive species, production of adenine is found to be strongly dominated by the radical-radical/radical-molecular reaction pathways. If all the reactions considered here contribute to the production of alanine and glycine, then neutral-neutral and radical-radical/radical-molecular pathways are both found to have a significant part in the production of alanine. Moreover, radical-radical/radical-molecular pathways also play a major role in the production of glycine. © 2012 National Astronomical Observatories of Chinese Academy of Sciences and IOP Publishing Ltd..


Gupta M.D.,Maharaja Manindra Chandra College
Transportation Research Part D: Transport and Environment | Year: 2014

Carbon footprint is intricately related with the consumption and lifestyle pattern of individuals. The transport sector is one of the major sectors that effects lifestyle in a significant way and is the major contributor towards the city emissions. This paper attempts to estimate the carbon footprint arising from household's use of road transport in the city of Kolkata across various income categories. The objective is to see how the footprint changes across income categories and also what factors drive changes in the footprint values across the defined income categories. The study has been based on primary surveys done across the city of Kolkata by choosing about 500 households across various income classes defined. Estimation of carbon footprint shows a clear picture of the relation between people's affluence and the average per capita footprint. It clearly shows that per capita footprint from transport use increases with income. Further results show that income, vehicle ownership and per capita transport expenditure has significant and positive impact on per capita footprint of households from road transport use. © 2014 Elsevier Ltd.


Chakrabarti S.K.,se National Center For Basic Science | Chakrabarti S.K.,Indian Center for Space Physics | Sasmal S.,Indian Center for Space Physics | Chakrabarti S.,Indian Center for Space Physics | Chakrabarti S.,Maharaja Manindra Chandra College
Natural Hazards and Earth System Science | Year: 2010

We show evidences for anomalous ionospheric behaviour in the signal of Indian navy VLF transmitting station named VTX due to earthquakes in the South Asian region. We concentrate on the variation of the D-layer preparation time (DLPT) and D-layer disappearance time (DLDT) in a period of sixteen months and study their average behaviors. We identify those days in which DLPT and DLDT exhibit significant deviations. Separately, we compute the energy release by earthquakes during this period and show that "anomalous VLF" days are associated with anomalous energy release. We find that the anomaly and the deviation of DLPT and DLDTs from the mean are linearly correlated. We discuss the predictability in this approach and compare with the terminator shift approach using the same set of data. © Author(s) 2010.

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